Conventionally, a vehicular electric fan system has been known that is designed to use an electric blower to distribute cooling air to a radiator for cooling water to cool an engine. The system also distributes cooling air to a vehicular air conditioning condenser (heat dissipater) for cooling the radiator and the condenser.
Suppose a case where such an electric fan system for a vehicle is applied to automobiles such as taxis or official cars which frequently use the electric fan system. In this case, it has been a general practice to employ an electric motor with a large electrical capacity and having an electric blower. It has also been the general practice to operate this electric motor using less than the rated electrical capacity to minimize deterioration of the electric motor to increase the life of the electric motor. However, the employment of such electric motor having large rated capacity may entail not only an increase in costs but also an increase in weight.
A brushless motor may also be employed as the electric motor for an electric blower for the purpose of increasing the life of the electric motor. As shown in FIG. 8, however, if the dimension of the radiator in the direction of vehicle width (lateral direction of the vehicle) is larger than the dimension of the electric blower impeller in the direction of vehicle width, a single electric blower will not be sufficient and will cause poor distribution of air blown to the radiator. This situation may leave some parts of the radiator not supplied with cooling air. Consequently, the cooling efficiency of the radiator will be decreased and hence the fuel economy also will be decreased.
If two or more electric blowers using a brushless motor are employed for solving the above-mentioned problem, it will be possible to optimize the distribution of air blown to the radiator and to supply the radiator with a sufficient amount of cooling air. However, this arrangement will require a control circuit with complex construction for controlling the brushless motors and, moreover, if two or more electric blowers having a brushless motor are employed, it will remarkably increase costs.
In view of the above-mentioned circumstances, the present invention has an object to provide an electric fan system for a vehicle which is capable of increasing the life without increasing the costs.